Target engagement and survival
In collaboration with the Inertial Fusion Group at
we perform research on direct-drive laser-IFE targets.
Power plant targets are cryogenically cooled (below 20 K)
capsules containing frozen DT. These targets must remain
exquisitely symmetric until they are irradiated simulateneously
by a number of intense lasers. We explore methods to track targets,
steer lasers onto them, steer the targets themselves, and ensure
survival during injection into a heated chamber.
Our research topics include:
- Target engagement
- Targets are injected at speeds of 50-400 m/s, and must be placed
at chamber center with an accuracy of 5 mm at a repetition rate of
5-10 per second. We track these targets using optical metrology systems
with accuracy better than 20 microns,
and feed this information into fast steering mirrors to allow precise
symmetric illumination of the target once it reaches the point of implosion.
- Target steering
- Direct drive targets are very light - typically just a few milligrams.
By placing an electric charge on the target, electric fields can be
used to steer the targets in flight. We are supporting General Atomics
in the development of an electrostatic steering system coupled with our
in-line target tracking technologies.
- Target survival
- Cryogenic direct-drive targets are very delicate.
If the outer surface temperature changes by more than 1-2° K during
transit through the chamber, then the target symmetry may degrade beyond the
point where successful implosion will ensue. We explore the thermal,
mechanical and phase-change behavior of direct-drive targets in order to
establish the design window for successful injection.
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